Large area material is understood to be for instance mattress fabric that is to be stretched around mattress cores. The sewing material concerned is of the type including at least one layer of a non-elastical material and one layer of an elastical material, for example foamed material, to be stitched together, wherein the stitched seams are arranged according to a predetermined pattern and particularly do not run exclusively in one direction which means that arbitrary sewing patterns are produced such as bias check or check patterns, circular saw or circular patterns and quite arbitrary contours. With sewing material of that kind the problem arises that due to the common drive for all the layers up to the sewing unit the elastical layer is subject to an expansion in the longitudinal or feeding direction. This elastical expansion is caused particularly by the fact that the sewing material, i.e. at least the two layers mentioned above, is drawn towards the pressure foot and into the sewing unit via a support. On this occasion, the tractive forces are transmitted to the sewing material which is stitched after it has passed through the sewing unit and is rolled onto a storage means. Doing this, the layer of elastical material rests either directly or indirectly on the support in front of the pressure foot and needle plate. Due to the friction existing in this area between said support and said layer of elastical material the latter is expanded and is stitched together with the layer of non-elastical material in this expanded condition. When the now stitched material leaves the multiple-needle sewing machine and is either rolled onto the storage means or cut to individual segments, the elastical material will tend to assume its original expansion, i.e. it will shrink again. Due to the shrinking of the elastical material said non-elastical material will form folds that disturb particularly the aesthetic appearance of the article produced from that material, for example a mattress.
Basing on this prior art, it is a problem of the present invention to provide a method and a multiple-needle sewing machine of the type concerned, wherein the formation of folds in the stitched product is prevented in a simple and inexpensive way.